Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$228.79	3.838%	$237.571	$237.57	$237.55	$237.60
Purchase #2	$47.26	11.659%	$52.77	$52.77	$52.75	$52.80
Purchase #3	$90.69	9.480%	$99.2874	$99.29	$99.30	$99.30
Purchase #4	$25.97	10.800%	$28.7748	$28.77	$28.75	$28.80
Purchase #5	$227.52	10.108%	$250.5177	$250.52	$250.50	$250.50
Purchase #6	$59.69	4.546%	$62.4035	$62.40	$62.40	$62.40
Purchase #7	$171.98	3.829%	$178.5651	$178.57	$178.55	$178.60
7 purchase totals =	$851.90		$909.8895	$909.89	$909.80	$910.00